Process for the Preparation of Biodiesel from Vegetable Oils Containing High FFA

Abstract

The present invention provides an improved process for the preparation of biodiesel from crude vegetable oils especially Jatropha ( Jatropha curcas ) and Karanja ( Pongamia pinnata ). In the preset invention the bio-active constituents, fatty acids and polar materials are selectively removed from the crude oils by liquid-liquid extraction with a polar solvent into the solvent phase in a non-destructive manner in specially designed equipment either in a batch mode or continuous mode and the oil left as residue is amenable for direct transesterification. After transesterification, the glycerol phase is separated and the crude biodiesel is neutralized, purified by adsorption of undesirable constituents like the residual glycerol, gums, soap, salts etc over a bed of adsorbent like Celite thereby circumventing the conventional water washing step. An alternative to the adsorbent method, the crude ester obtained after transesterification is purified using partition with aqueous solvent to biodiesel which meets the International specifications.

1 . A process for the preparation of biodiesel from crude vegetable/animal oils containing high free fatty acid (FFA), said process comprising the steps of:
 a) deacidifying the crude vegetable oil containing high FFA by liquid-liquid extraction with polar organic solvent in extraction equipment either in a batch or continuous mode to obtain a resultant oil raffinate and an extract containing FFA, polar materials and bioactive components;   b) esterifying in situ said extract containing FFA with an acid catalyst to obtain a resultant esterified extract and mixing it into the resultant oil raffinate, followed by filtration to remove the free suspended solids; and   c) subjecting a resultant oil filtrate obtained in step (b) to transesterification using methanol, in the presence of a base catalyst, followed by the separation of crude ester from a glycerol phase and purifying the crude ester either by celite adsorption after neutralization and solvent removal or directly by liquid-liquid extraction using about 1-20% aqueous polar organic solvent with a ratio of crude ester to solvent in the range of about 1:1 to about 1:4 to separate out the desired pure biodiesel phase and filtering the left out solvent phase after neutralization to obtain an impure ester and recycling it to step (a) along with crude oil feed for further use.   
   
   
       2 . The process according to  claim 1  wherein the vegetable oil used is selected from Jatropha ( Jatropha  cures) and Karanja ( Pongamia pinnata ). 
   
   
       3 . The process according to  claim 1  wherein the FFA content of the vegetable/animal oil is in the range of about 2-30%. 
   
   
       4 . The process according to  claim 1 , wherein the liquid-liquid extraction used in step (a) is carried out at atmospheric pressure and at or below the boiling point of the organic polar solvent. 
   
   
       5 . The process according to  claim 1  wherein the polar organic solvent used is methanol or ethanol. 
   
   
       6 . The process according to  claim 1  wherein the FFA content in oil raffinate obtained in step (a) is reduced to a value in the range of about 0.2-1%. 
   
   
       7 . The process according to  claim 1  wherein the proportion of water used in aqueous organic polar solvent in step (c) for purification is in the range of about 1-15%. 
   
   
       8 . The process according to  claim 1  wherein the ratio of crude ester to aqueous polar organic solvent used in step (c) is in the range of about 1:0.5 to about 1:3. 
   
   
       9 . The process according to  claim 1  wherein the crude alkaline ester and aqueous polar organic solvent used in step (c) are mixed under stirring at a refluxing temperature or under a simple warm condition. 
   
   
       10 . The process according to  claim 3  wherein the FFA content of the vegetable/animal oil is in the range of about 1-10%